1. Field of the Invention
The present invention relates to a route search method in a navigation system, and more particularly to a route search method in a navigation system in which POI (Point of Interest) information regarding POIs is incorporated in map information, and a route up to a specified POI is searched for.
2. Description of the Related Art
In a navigation system, the position of a vehicle is detected and map data around the vehicle position is read out of a map storage medium such as a CD-ROM or DVD. Then, in the Map Guide Mode, a map around the vehicle and a guide route are generated and drawn on a display screen based on the map data and guide route data. At the same time, a mark of the vehicle position is displayed on the map at a predetermined point in overlying relation. As a vehicle""s current position changes with movement of the vehicle, the map is scrolled with the vehicle position mark fixed at the center of the screen in its lower area, allowing the driver to always confirm a detailed map around the vehicle position at a glance. In the Arrow Guide Mode, a guide route, roads crossing the guide route, and so on are displayed in a simplified form, and the direction of travel at an intersection is indicated by an arrow. Also, the distance to the next intersection, the direction toward the destination, the distance to the destination, and so on are displayed. In addition, the direction of travel at an intersection is guided by a voice output.
To implement route guidance in the Map Guide Mode or the Arrow Guide Mode, a destination must be inputted to search for the guide route up to the destination. Various methods are available for inputting the destination. For example, there is a method of inputting the destination using a POI (Point of Interest). The destination can be inputted using a POI by;
(1) entering the Place Name of a POI representing the destination, or
(2) entering the Place Type (category) of a POI representing the destination to display a candidate list of Place Names, and selecting one Place Name corresponding to the destination from the candidate list.
To input the destination by the above method (2), the user operates a menu key on a remote control to display a main menu on a screen (see FIG. 6A), and selects the menu item xe2x80x9cDestxe2x80x9d from the main menu. With such a user""s operation, the navigation system displays a screen image of xe2x80x9cFind Destination byxe2x80x9d for specifying a manner of inputting the destination, as shown in FIG. 6B. Then, upon the user selecting the menu item xe2x80x9cPoint of Interestxe2x80x9d, the navigation system displays two menu items, xe2x80x9cPlace Namexe2x80x9d and xe2x80x9cPlace Typexe2x80x9d, as shown in FIG. 6C. Selecting the menu item xe2x80x9cPlace Typexe2x80x9d causes the navigation system to display a screen image of xe2x80x9cSelect Categoryxe2x80x9d that is a list of categories, as shown in FIG. 6D. With a certain category (e.g., shopping) selected from the category list, the navigation system displays an alphabet/numeric keyboard for prompting the user to enter the city name, as shown in FIG. 6E. Upon the user entering several letters of the spelling of the city name from the beginning, a list of city names having those letters is displayed in a scrollable manner. The user selects one desired city name (e.g., Costa Mesa) from the list, or enters the full spelling of the city name.
After completing the entry of the city name, the navigation system displays a list of all POIs in a scrollable manner, which exist in the city and belong to the specified category, as shown in FIG. 6F. Selecting a desired POI (e.g., Triangle Square) from the POI list causes the name, address, telephone number, etc. of the selected POI to be displayed as shown in FIG. 6G. If the displayed POI is correct as the destination, the user selects an item xe2x80x9cOK to Proceedxe2x80x9d to confirm the displayed POI as the destination. Thereafter, the navigation system searches for a guide route from the current position of the vehicle and displays the guide route. In the case of inputting the destination by the above method (1), the user selects the menu item xe2x80x9cPlace Namexe2x80x9d in FIG. 6C, and then directly enters the name of a desired POI.
At some POIs, such as a large shopping mall or a baseball stadium, there exist many gateways (entrances and exits). In a conventional POI database structure, however, only one road link (gateway) is stored corresponding to one POI. Accordingly, regardless of whether the vehicle is positioned on the north, south, east or west of the target POI, the road link (gateway) finally obtained as a result of the route search has been always the same. In other words, a conventional navigation system has the problem that even when there is another gateway nearer to the vehicle position than the one gateway set in the system, the vehicle is not guided to the nearer gateway, but is always guided to the one gateway taking a longer distance.
Also, although a shopping mall (parent POI) usually has many shops (child POIs), the conventional navigation system always guides the vehicle to the same gateway no matter which one of the shops (child POIs) is the destination. Thus, another problem has been experienced in that the vehicle is not always guided to a gateway nearest to the target shop (child POI).
Therefore, one object of the present invention is to, when a POI having a plurality of gateways is set as the destination, enable a vehicle to be guided to a gateway nearest to the current position of the vehicle.
Another object of the present invention is to, when a parent POI has a plurality of gateways, enable a vehicle to be guided to the gateway nearest to a target shop (child POI).
According to the present invention, the first object is achieved by a route search method in a navigation system in which POI (Point of Interest) information regarding POIs is incorporated in map information and a route up to a specified POI is searched for, the method comprising the steps of (1) when a POI has a plurality of gateways, incorporating identification data for road links connected respectively to the gateways in the POI information; (2) when a plurality of road links are stored corresponding to a POI set as a destination, searching for a route up to each of the road links; and (3) determining an optimum one of the found routes as a guide route.
Also, according to the present invention, the second object is achieved by a route search method in a navigation system in which POI (Point of Interest) information regarding POIs is incorporated in map information and a route up to a specified POI is searched for, the method comprising the steps of (1) when a relationship between a POI and shops in the POI is defined as a parent-child relation, storing child POIs in corresponding relation to a parent POI and storing one road link in corresponding relation to each child POI as part of the POI information; and (2) when one child POI is set as a destination, searching for a guide route up to the road link corresponding to the set child POI.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings.